A circular knitting machine can control the yarn loop density of fabrics by adjusting the position of cams. The circular knitting machine has a plurality of cams to adjust the yarn loop density at different locations of a fabric.
Conventional techniques mostly aim to adjust the position of a single cam. For instance, R.O.C utility patent Nos. M251848 and M247597 granted to the Applicant disclose an adjustment method that has a regulation wheel turnable to drive a slider to adjust the position of a cam. The adjustment task is done manually. When the number of cams to be adjusted is great, to do adjustment takes a great deal of manpower and time. Human errors also are prone to occur. To remedy this problem, U.S. Pat. No. 5,511,392 discloses a method which has an elevating means to adjust the vertical position of a mounting plate, thereby saddle seats which hold cams and are located on the mounting plate can be moved up or down. While it can adjust the vertical positions of multiple cams, it cannot fine tune the yarn loop density of individual fabric zones.
U.S. Pat. No. 7,065,988 discloses a device aiming to alter stitch tightness of circular knitting machines. It is coupled with a movement adjuster connecting to a slider which is slidable on a cam box of a knitting machine and supports a knockover cam. The movement adjuster includes an actuator connecting to an adjustment cam, and may be driven to rotate the adjustment cam about its axis to a selected angle. The adjustment cam has an external active profile and two cam followers that are located on the slider. When the adjustment cam is driven by the actuator, the two cam followers adjust the cam position on the slider. It aims to adjust the position of a single cam without relying on moving up or down of the mounting plate. The actuator also provides driving to eliminate the uncertainty of human control and tedious operation. The adjustment cam is an eccentric cam in contact with the two cam followers. The contact positions require precise calculation and fabrication to ensure that the cam can provide accurate movement. Moreover, the adjustment cam is embedded deeply in the saddle seat. Its size and moving track range are restricted. Thus fabrication is difficult.